hello,
I need some help. operating system that provide interface between hardware and application software. A shell is a program that provides , text-only user interface for Linux operating system. A shell script is a text file that contains a sequence of Linux commands

how does shell program work in embedded Linux operating system ?

 

Unix like operating systems (which includes Linux) have the concept of a kernel and a shell (from a nut, which has a kernel and a shell). There are a number of shells csh, ksh, korn, bash, pretty much all linux's use bash. It is the job of the shell to execute a shell script which is nothing more than a set of shell commands. In fact anything you can put in a script you can just type at the command line, however it is often pretty inconvenient to do that.

So as long as you can cause the shell in your embedded linux to read a file (i.e. mount a device or whatever) you can make the file executable (chmod +x) and then execute it from the command line

 

Do you have in mind something like Android embedded in a cell phone or tablet?

Generally device manufacturers won't give you a shell. It is however possible but difficult to install one. A preliminary step is known as "rooting" or "jailbreaking" the device. This allows you to install unsigned software onto your device. Once you have the ability to install unsigned software, you can install a shell. If you make any mistakes it's likely that your device will be permanently broken.